1. FIELD OF THE INVENTION
The present invention pertains generally to CO.sub.2 lasers and more particularly, to RF excited CO.sub.2 waveguide lasers.
2. PRIOR ART
The principles of a waveguide gas laser were first discussed by Marcatili and Schmeltezer in a 1964 article in the Bell Systems Technology Journal, volume 43, page 1783. Waveguide operation of a helium neon laser was reported by P. W. Smith in a 1971 article in the Applied Physics Letters, volume 19, page 132. CO.sub.2 waveguide lasers have been reported in a 1972 article by Bridges, Berkhardt and Smith in Applied Physics Letters, volume 20, page 403, in a 1972 article by Jensen and Tobin in the I.E.E.E. Journal of Quantum Electronics, volume QE8, page 34, in a 1972 article by Chester and Abrahms in the Applied Physics Letters, volume 21, page 576 and in a 1972 article by Berkhardt, Bridges and Smith in Optical Communications, volume 6, page 193. RF excited CO.sub.2 waveguide lasers have been disclosed in a 1978 article by Lachambre, MacFarlane, Otis, and Lavigne in Applied Physics Letters, volume 32, page 652 and in U.S. Pat. No. 4,169,251 by Laakmann issued Sept. 25, 1979. Further significant improvements in RF excited CO.sub.2 waveguide lasers are disclosed in U.S. patent application Ser. No. 78,343 filed Sept. 24, 1979 by the present applicants and the disclosures contained therein are incorporated herein in their entirety by reference.
In many industrial applications of CO.sub.2 lasers it is highly advantageous to have a self-contained laser tube that does not require an input of gas during operation. Such sealed-off CO.sub.2 lasers do not require auxillary gas cylinders and vacuum pumps and thus lend themselves more readily to portable operation. However, one of the main problems associated with sealed-off CO.sub.2 lasers is that of maintaining stable long term operation despite factors which tend to destabilize the gas chemistry such as CO.sub.2 dissociation, O.sub.2 consumption, and outgassing.
The problem of stable long term operation of sealed-off CO.sub.2 laser tubes has been the subject of extensive investigation by Witteman, reported in the following articles: 1965 Physics Letters, volume 18, page 125; 1966 Phillips Research Report, volume 21, page 73; 1966 I.E.E.E. Journal of Quantum Electronics, volume QE-2, page 375; 1967 Applied Physics Letters, volume 10, page 347; 1967 Phillips Technical Review, volume 28, page 287; 1967 Applied Physics Letters, volume 11, page 337; 1968 I.E.E.E. Journal of Quantum Electronics, volume QE 4, page 786; and 1969 I.E.E.E. Quantum Electronics, volume QE 5, page 92; and by Carbone in the following articles: 1967 I.E.E.E. Journal of Quantum Electronics, volume QE 3, page 373; 1968 I.E.E.E. Journal of Quantum Electronics, volume QE 4, page 102; and 1969 I.E.E.E. Journal of Quantum Electronics, volume QE 5, page 48. It is interesting to note that Witteman discloses a system for extending the life of sealed-off CO.sub.2 laser tubes which relies on the admixture of a small amount of H.sub.2 O, H.sub.2, or H.sub.2 and O.sub.2 to the standard CO.sub.2 laser gas mix.